sub build underway christmas 2011

Discussion in 'Boat Design' started by tugboat, Jan 5, 2012.

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  1. tugboat

    tugboat Previous Member

    the nice thing about the great lakes is thier clarity--depth to about 50 ft or so clear caribean quality fresh water-- i can see down about 60 ft when swimming on the surface sometimes the water is so clear you think" i can reach down and touch that rock" when you go to do so- you find your diving 20 ft..its really something...clear cool drinkable water in most areas..especially superior where the waters 600 ft deep...this was why the sub idea also was so appealing..on the ocean or anywhere else the views wouldnt have been worth building a sub for... this year i swam right over a an wooden wreck in about 30 ft of water--to get a better look i just donned my mask and down i went...it was awesome seeing that 120 year old boat -its bones sitting on the bottom-some steel parts still intact because of the the fresh water and no crustaceans other than the few zebra mussels|(which are dying out it appears)...
     
  2. tugboat

    tugboat Previous Member

    :!::!::!::!::!::!::!:
     
  3. BATAAN
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    BATAAN Senior Member

    One would hope the Z mussels go away and never return.
     
  4. BPL
    Joined: Dec 2011
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    BPL Senior Member

    The quagga mussels will be worse than the zebra mussels. The quagga mussel outcompete the zebra mussels and filter out food that diporeia need. Diporeia are necessary food for fish. The increased water clarity now from the quagga mussel will also increase algae blooms. The worst is the blue-green microcystis.
     
  5. BATAAN
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    BATAAN Senior Member

    All I can say is human short-sightedness and lack of care keeps getting us in terrible messes that kill lots of things around us.
     
  6. Boston

    Boston Previous Member

    I"m not seeing any external anything other than a coning tower and a few fins.

    [​IMG]

    Looks like a smooth hull form that requires everything to be internal.

    Even if you put the hatch in the shade on a hot day the air temp will still effect it. Granted not as much as if it was directly in the hot sun but still there's always going to be an expansion joint needed between the two materials unless you encaplulate one entirely within the other, as is the case with rebar . Even then oxidation will degrade the point of contact from the word go as concrete wicks moisture really well. Which is another point that needs to be considered, not only will the outside need to be sealed perfectly but the inside as well, along with the through hulls, Even a pin hole will wick moisture throughout the concrete.

    I guess the next question is why not just build it out of steel ?
     
  7. BATAAN
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    BATAAN Senior Member

    The hull as drawn in not a cylinder, but a complex developed shape with double curvature at all points. This is good for compressive strength as "it's all arch".
    If the material is perfectly executed in some sort of pressure mold and the armature is good it would obviously work as a pressure vessel for outside pressure since it's all arched and it's all compression.
    It's a wonderful theory.
    The devil is in the details of making it actually work with real people using real tools on a real low budget.
    A double rebate joint can be designed to join a steel hatch/trunk to the concrete hull, but this inevitably creates a stress riser at this point. Such a joint would have several inches of sealant plus an O-ring in a locking wedge groove.
    I've serviced literally hundreds of shaft stuffing boxes and seen the stuffing blown out from an 8" prop shaft when a 300 pound depth charge went off much too close and the amount of water pouring in even a small 1.5" shaft at near-surface pressure is hard to keep ahead of if the shaft is spinning continuously.
    This is why modern very small subs put the motors and most everything else outside and under pressure.
    This all seems do-able with diligence but other things are in play.
    Reading the tech articles bouncing around one phenomenon that comes up is spalling, where concrete under great compression actually makes the structure get slightly smaller and this compressive moment at the inner surface makes small thin chunks fly off at very high velocity, kind of like shell fragments from artillery.
    In "Das Boot" they show the rivets of the ring frames losing their heads which go banging off the inside like bullets if you want to get the effect.
    If ballast tanks are inside, it's a slow process blowing them out under pressure as valve sectional area is much less. Any sub like this should be ballasted slightly positive, then use the planes alone to pull it down. This is box-standard for the first test dive of any submarine, including the very largest.
     
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  8. gundagai
    Joined: Jan 2012
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    gundagai Junior Member

    More to argue about

    Crushed drum seen it and understand it. Now here is another concrete submarine v, Ice aircraft carrier as proposed by the english to close the air gap on the nazi subs. now who is crazy. Ice crete?
    I understsand the problems of disimilar materials as previously stated.
    I personally would use steel because I understand it even though the drum collapsed.
    As for if you can not draw it you can not make it... boats built in the eighteen hundreds were built from half models no drawings.
    Then there is the under water crossing from Swedan to Norway I thinks concrete to last one hundred years under water.
    These are just a few things I would like your comments on!
    Now say tugboat does build this submarine how the heck is he going to sink it concrete is boyant compared to steel?
    So lets not worry about what if just solutions and how too. would be good!
     
    Last edited: Jan 21, 2012
  9. Stumble
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    Stumble Senior Member

    After having done some research on this, I onestly think a concrete sub can work, and can be made to work safely. That being said, I don't think that a teardrop shaped hull is reasonable for a home builder, and the dangers of trying a home build preassure vessel are much to high to ever be considered reasonable.

    My solution would be to use commercially available high preassure concrete pipe, available off the shelf in up to 120" round, and 50' long. These are manufactured by spinning enormous drums at high speed while introducing the concrete so that centrifical force pushed the concrete to the sides in a predictable and repeatable fashion. But it does limit you to primarily round or elliptical shapes.

    Boston,
    You have raised the concern of hatches, and the different thermal expansion of dissimilar materials a number of times. I don't mean to be dismissive, but there are off the shelf solutions to this available for around $500. The same concrete pipe manufacturers that make the high preassure pipe also make preassure tested hatches available off the shelf.

    All of the components I am discussing have a minimum working preassure, verified at 400psi, or a little over 27 atmospheres. Which would give a maximum dive depth of 891 foot. Which is much deeper than I at least would expect out of private submarine.
     
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  10. bntii
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    bntii Senior Member

    Stumble- the working pressure of that pipe may well be far higher than the external pressure it can resist.
    Look to our discussion of the oil drum for instance or many hose products with high working pressures though have no resistance to crushing.

    The pipe is designed to resist soil pressure.
    I looked around and could not quickly find a spec for external pressure resistance though I am seeing design loads to resist in the range of ~10-20 psi?
    I should not be to tough to find the external pressures the tubes can resist.

    Here is a document which covers the design brief for many of these products:

    http://www.ives.edu.mx/bibliodigita...e los fluidos/Buried Pipe Design/35030_05.pdf

    These pipes appear the be constructed with highly tensioned wire wrap to resist internal pressures while the concrete resists crushing from the soil.
     
  11. BATAAN
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    BATAAN Senior Member

    If a commercial concrete pipe section could work, possibly steel ends (incorporating all the usual fixes for through hulls etc) flanged over the concreted pipe ends in such a way as the pressure made them tighter and compressed and O-ring or some such, would solve the hatch/prop/planes issues.
    I believe if a pipe is rated at 400 psi internal pressure and has a thick and buckle-resistant wall (not oil drum) would it not have even more resistance to external pressure if it were equally distributed?
     
  12. gundagai
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    gundagai Junior Member

    ground crushing

    I worked underground and saw the effects of crushing. Last resorts were to line the tunnel with steel and then spray concrete over the steel. Worked better than steel rsj's that would crush and distort from the pressure. I would build my submarine out of steel if I were to do it.
     
  13. Boston

    Boston Previous Member

    hmmmmmmm, concrete is basically a compression material. Tension, not so much. So if its designed to withstand x amount of tension forces it will most likely withstand 5x amount of compression. But city water pressure is typically not more than about 100 lbs at the street and about 40 at the faucet. So those huge concrete water mains although they do have to hold a lot of weight and be able to resist the crushing forces of the fill around them really don't need that much strength. I notice the ones they are putting in just a mile or so from here are 5' diameter but only about 4" in wall thickness, and they bury them about 6' down. which just isn't that much dirt over them. They also break one or so a day just handling it. Got a whole pile of damaged ones I drive by almost every day

    I'm not a utilities contractor although I've been thinking about it since the residential custom homes market is so flat, but I'd have to see some pretty convincing detail drawings of this plan before I'd trust it very far.

    I'm still not sure why concrete, isn't steel or eve carbon fiber a much easier choice.
     
  14. BATAAN
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    BATAAN Senior Member

    Concrete because "cheap" and "easy".
     

  15. gundagai
    Joined: Jan 2012
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    gundagai Junior Member

    What a contradiction in quotes
    Easy and everyone would be doing it
    Cheap the chinese would be doing it
    Mmmmmmm
     
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